CN107132455A - A kind of grounding net of transformer substation performance estimating method injected based on ground line current - Google Patents

Abstract

This application discloses a method for evaluating the performance of a substation grounding grid based on ground wire current injection. The method includes: obtaining substation parameters and the original shunt coefficient k _e2 of the substation grounding grid; selecting an overhead ground wire of the substation, and Line injection current I _w , respectively measure the total current I _w1 flowing out of the line connected to the substation and the current I _N flowing out of the neutral point of the transformer, and calculate the grounding current I of the substation grounding network according to the current I _w , I _w1 and I _{N g} , calculate the shunt coefficient k _e1 of the substation grounding grid according to the current I _g and I _w , calculate the variation of the shunt coefficient k _e1 and the original shunt coefficient k _e2 , and evaluate the safety performance of the substation grounding grid. The evaluation method provided by this application does not need to measure the grounding resistance of the substation, which greatly reduces the measurement workload, and this method can be carried out during the normal operation of the substation without power failure.

Description

A Performance Evaluation Method of Substation Grounding Grid Based on Ground Wire Current Injection

technical field

The invention relates to the technical field of substation grounding grids, in particular to a method for evaluating the performance of substation grounding grids based on ground wire current injection.

Background technique

The grounding grid plays a very important role in the safe operation of the power system. It not only provides a common signal reference ground for various electrical equipment, but more importantly, it can quickly discharge the fault current and reduce the rise of the ground potential when the system fails. Therefore, the grounding performance of the grounding grid is directly related to the personal safety of the power system workers and the safety and normal operation of various electrical equipment. In recent years, due to the rapid growth of my country's electricity demand, the scale and capacity of the power system have expanded rapidly, and the grounding short-circuit current has become larger and larger, thus putting forward higher requirements for the safety and reliability of the grounding grid. IEEE stipulates that the substation grounding resistance must meet R≤2000/Ig, where Ig is the maximum ground fault asymmetrical current that enters the ground through the grounding grid.

At present, the method for evaluating the performance of the substation grounding grid is mainly to measure the grounding resistance of the substation. The commonly used method for measuring the grounding resistance of the grounding grid is the three-pole method. The method of testing grounding resistance with three electrodes composed of auxiliary pole P1 and current auxiliary pole P2 generally adopts the straight line method to arrange the electrodes, as shown in Figure 1. When measuring, the external power supply is connected, and the test current is injected by the grounding grid G (equivalent to a hemispherical electrode), and a loop is formed between the grounding grid G, the current auxiliary pole P2 and the ground, and the current value of the loop is obtained by measuring the current value of the loop with an ammeter, and using the voltage The meter measures the voltage value between the grounding grid G and the voltage auxiliary pole P1, and the grounding resistance value can be obtained by comparing the voltage value with the current value.

However, when using the three-pole method to measure the grounding resistance of the grounding grid, it is necessary to lay hundreds of meters or even several kilometers of voltage and current leads, and it is necessary to measure the soil structure and soil resistivity, and the workload is very heavy. There are also many factors affecting the three-pole method measurement method, resulting in large measurement errors.

Contents of the invention

The invention provides a substation grounding network performance evaluation method based on ground wire current injection to solve the problems of large workload and large measurement error in the current measurement method.

The invention provides a method for evaluating the performance of a substation grounding grid based on ground wire current injection, the method comprising:

Obtain the substation parameters and the original shunt coefficient k _e2 of the substation grounding grid;

Selecting an overhead ground wire of the substation, and injecting a current _{Iw into the overhead ground wire, respectively measuring the total current I w1 flowing} out of the line connected to the substation and the current I _N flowing out of the neutral point of the transformer;

According to the formula Ig= _Iw - _Iw1 -I _N , the grounding current _Ig of the _substation grounding network is obtained;

According to the formula k _e1 =I _g /I _w , the shunt coefficient k _e1 of the substation grounding grid is obtained;

The safety performance of the substation grounding grid is evaluated by comparing the distribution coefficient k _e1 with the original distribution coefficient k _e2 .

Optionally, the acquisition of substation parameters specifically includes:

The substation includes n overhead ground wires and m return cables, where n≥1 and m≥0.

Optionally, the measuring the total current I _w1 of the lines connected to the substation specifically includes:

Measuring the current I _w2 flowing out of n-1 overhead ground wires connected to the substation;

Measure the current I _w3 flowing out of the m return cables connected to the substation.

Optionally, the comparison of the distribution coefficient k _e1 and the original distribution coefficient k _e2 to evaluate the safety performance of the substation grounding grid specifically includes:

Calculate the size variation of the shunt coefficient k _e1 and the original shunt coefficient k _e2 ;

If the variation of the shunt coefficient k _e1 and the original shunt coefficient k _e2 is greater than 20%, it is determined that there may be a fault in the grounding grid of the substation;

If the variation of the distribution coefficient k _e1 and the original distribution coefficient k _e2 is less than or equal to 20%, it is determined that the performance of the substation grounding grid is good.

The technical solution provided by the invention may include the following beneficial effects:

The method for evaluating the performance of a substation grounding grid based on ground wire current injection provided by the present invention includes: obtaining substation parameters, calculating the original shunt coefficient k _e2 of the substation grounding grid, selecting an overhead ground wire of the substation, and Inject the current I _w into the overhead ground wire, measure the total current I _w1 flowing out of the line connected to the substation and the current I _N flowing out of the neutral point of the transformer, and calculate the substation grounding according to the formula I _g = I _w -I _w1 -I _N The substation grounding grid current I _g is calculated according to the formula k _e1 = I _g /I _w to obtain the shunt coefficient k _{e1 of the substation grounding grid. The shunt coefficient k e1 and} the original shunt coefficient k _e2 are compared to evaluate the safety performance of the substation grounding grid. The grounding network performance evaluation method based on the current distribution measurement proposed by the present invention does not need to measure the grounding resistance of the substation, which greatly reduces the measurement workload; and this method can be carried out during the normal operation of the substation without power outage; The results are less affected by season and climate.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention.

Description of drawings

In order to illustrate the technical solution of the present invention more clearly, the accompanying drawings that need to be used in the embodiments will be briefly introduced below. Obviously, for those of ordinary skill in the art, on the premise of not paying creative labor, Additional drawings can also be derived from these drawings.

Fig. 1 is a schematic diagram of a method for measuring the grounding resistance of a substation grounding grid in the prior art;

Fig. 2 is a schematic flow chart of a substation grounding grid performance evaluation method based on ground wire current injection provided by an embodiment of the present invention;

3 is a measurement schematic diagram of a substation grounding grid performance evaluation method based on ground wire current injection provided by an embodiment of the present invention;

Fig. 4 is a detailed flow diagram of S200 in a substation grounding grid performance evaluation method based on ground wire current injection provided by an embodiment of the present invention;

Fig. 5 is a detailed flowchart of S500 in a substation grounding grid performance evaluation method based on ground wire current injection provided by an embodiment of the present invention.

detailed description

Referring to FIG. 2 , it is a flowchart of a method for evaluating the performance of a substation grounding grid based on ground wire current injection provided by an embodiment of the present application.

S100: Obtain the substation parameters and the original shunt coefficient k _e2 of the substation grounding grid.

Specifically, the number of overhead ground wires and cables in the substation is obtained, and the substation includes n overhead ground wires and m return cables, where n≥1, m≥0. A substation generally includes multiple loops, and each loop is connected to more than two overhead ground wires. Before evaluating the performance of the substation grounding grid, first obtain the number of overhead ground wires and cables connected to the substation and the original shunt coefficient of the substation grounding grid k _e2 .

S200: Select an overhead ground wire of the substation, inject a current _{Iw into the overhead ground wire, and measure the total current I w1 flowing} from the lines connected to the substation and the current I _N flowing from the neutral point of the transformer respectively.

Specifically, select an overhead ground wire on a return line of the substation to be evaluated, and inject current I _w into the overhead ground wire, as shown in Figure 3, connect an external current source to a certain overhead ground wire in the substation, use The current probe C ₁ measures the current _Iw that enters the substation through the overhead ground wire that injects current through the overhead ground wire. The current I _w entering the substation through the overhead ground wire is shunted by the overhead ground wire, cable, transformer neutral point and grounding grid, and the current I _w1 flowing out of the line (overhead ground wire and cable) connected to the substation is measured with a current probe , use the current probe C ₃ to measure the current I _N flowing out of the neutral point of the transformer, while the grounding current of the grounding network cannot be directly measured, but can be calculated.

Refer to Fig. 4 for the specific method of measuring the current I _w1 of the lines (overhead ground wires and cables) connected to the substation.

S201: Measure the current I _w2 flowing out of n-1 overhead ground wires connected to the substation.

S202: Measure the current _Iw3 flowing out of the m-circuit cables connected to the substation.

Specifically, one return line is usually connected with more than two overhead ground wires, and the overhead ground wires are connected in parallel and located on both sides of the tower. While the substation contains n overhead ground wires (n≥1), the current I _w2 flowing out of n-1 overhead ground wires is measured with a current probe C ₂ . In addition, the substation is usually equipped with m-circuit cables (m≥0), and the cables can also play a role in shunting. If the substation to be evaluated does not contain cables, it is not necessary to measure the current; if the substation contains m-circuit cables, the cable Use the current probe C ₄ to measure the total current I _w3 flowing out of the m-circuit cable connected to the substation.

When the substation is not equipped with cables, the size of the current I _w3 is zero, and the total current I _w1 = I _w2 flowing out of the lines (overhead ground wires) connected to the substation at this time; when the substation is equipped with cables, the lines connected to the substation ( The total current I _w1 flowing out from overhead ground wires and cables) = I _w2 + I _w3 . Therefore, the current flowing out of the line connected to the substation should depend on the situation.

S300: Calculate and obtain the grounding current I _g of the substation grounding grid according to the formula I _{g =} I _w -I _w1 -IN.

Specifically, the current Iw entering the substation through the overhead ground wire is _shunted by the overhead ground wire, cable, transformer neutral point and ground grid, and the current flowing out of the overhead ground wire, cable and transformer neutral point can be measured by the current probe to obtain the current It can be measured by the current probe that the current flowing out of the line (overhead ground wire and cable) connected to the substation is I _w1 = I _w2 + I _w3 , the current flowing out of the neutral point of the transformer is I _N , and the grounding grid enters the ground The current cannot be measured, but it can be calculated by formula (1):

S400: Calculating according to the formula k _e1 =I _g /I _w to obtain the shunt coefficient k _e1 of the substation grounding grid.

Specifically, according to the calculated grounding current _{Ig of the grounding grid, the shunt coefficient k e1 of} the substation grounding grid can be obtained, and the calculation formula is:

Substituting formula (1) into formula (2), we can get:

S500: Comparing the shunt coefficient k _e1 with the original shunt coefficient k _e2 , evaluating the safety performance of the substation grounding grid.

Specifically, the calculated shunt coefficient k _e1 of the substation grounding grid to be evaluated is compared with the original shunt coefficient k _e2 to evaluate the performance of the substation grounding grid. Among them, the method steps to obtain the original shunt coefficient k _e2 are the same as the method steps to obtain the shunt coefficient k _e1 , the key is to select the same return line of the substation and inject current on the same overhead ground line of the return line before the new substation is built and used In the test, the original shunt coefficient k _e2 obtained in this way can be compared with the shunt coefficient k _e1 obtained after the substation has been running for a period of time, so that the performance of the substation grounding grid can be evaluated.

As shown in Figure 5, the specific steps to evaluate the performance of the substation grounding grid according to the shunt coefficient are as follows:

S501: Calculate the magnitude change of the distribution coefficient k _e1 and the original distribution coefficient k _e2 .

S502: If the variation of the distribution coefficient k _e1 and the original distribution coefficient k _e2 is greater than 20%, it is determined that there may be a fault in the substation grounding grid.

S503: If the variation of the distribution coefficient k _e1 and the original distribution coefficient k _e2 is less than or equal to 20%, it is determined that the performance of the substation grounding grid is good.

Specifically, compare the size of the distribution coefficient k _e1 and the original distribution coefficient k _e2 , and calculate the change in the size of the distribution coefficient k _e1 and the original distribution coefficient k _e2 (k _e2 -k _e1 )/k _e2 , if the distribution coefficient k _e1 and the original The variation of the shunt coefficient k _e2 (k _e2 -k _e1 )/k _e2 is greater than 20%, that is, the shunt coefficient becomes significantly smaller, which indicates that there may be a fault in the grounding grid of the substation, and further testing is required; if the shunt coefficient k _e1 is the same as the original The variation of the shunt coefficient k _e2 (k _e2 -k _e1 )/k _e2 is less than or equal to 20%, that is, the shunt coefficient does not change much, which indicates that the performance of the substation grounding grid is good.

This application uses a specific example to illustrate the substation grounding grid performance evaluation method based on ground wire current injection provided by this application.

Before the Funing Station was put into use, a current injection test was carried out on an overhead ground wire of Fuwu-Wuzhou Line A. The current Iw entering the substation was _1.1kA on this overhead ground wire, and at the same time, the current Iw flowing out of another overhead ground wire of Fuwu-Wuzhou Line A was The current I _w2 is 0.2kA, the current I _w3 flowing out of the overhead ground wire on other lines connected to the substation is 0.2kA, and the current I _N flowing out of the neutral point of the transformer is 0.1kA, so the original shunt coefficient k _e2 is calculated to be 54.5 %. After the substation has been in operation for 2 years, the current injection test is carried out again on the same overhead ground wire. With the same calculation method, the shunt coefficient k _e1 of the substation grounding grid is calculated to be 12.2%, and the shunt coefficient k _e1 is much smaller than the original shunt coefficient k _e2 ( (k _e2 -k _e1 )/k _e2 >20%), so it can be determined that there may be a fault in the grounding grid of the substation, and further detection is required.

The application provides a substation grounding network performance evaluation method based on ground wire current injection. The method includes: obtaining substation parameters and the original shunt coefficient k _e2 of the substation grounding network; selecting an overhead ground wire of the substation, and The current I _w is injected into the substation, and the current I _w is shunted through the overhead ground wires, cables, transformer neutral points and grounding grids connected to the substation. The substation includes n overhead ground wires and m return cables, where n≥1,m ≥0, respectively measure the total current I _w1 flowing out of the lines connected to the substation and the current I _N flowing out of the neutral point of the transformer, and the total current I _w1 flowing out of the lines connected to the substation includes n-1 overhead wires connected to the substation The current I _w2 flowing out and the current I _w3 flowing out of the m-circuit cable connected to the substation, that is, I _w1 = I _w2 + I _w3 ; according to the formula I _g = I _w -I _w1 -I _N , the grounding current of the substation grounding network can be obtained I _g ; according to the formula k _e1 =I _g /I _w to calculate the shunt coefficient k _e1 of the substation grounding network; calculate the variation of the shunt coefficient k _e1 and the original shunt coefficient k _e2 , according to the shunt coefficient k _e1 and the original shunt coefficient k The variation of _e2 evaluates the safety performance of the substation grounding grid. The method for evaluating the performance of the substation grounding grid based on ground wire current injection proposed in this application does not need to measure the grounding resistance of the substation, which greatly reduces the measurement workload. Moreover, the method can be carried out during normal operation of the substation without power failure. In addition, when evaluating the performance of the grounding grid through grounding resistance, the grounding resistance of the line pole tower and the grounding resistance of the substation grounding grid change with the season and climate at the same time, and the measurement results are greatly affected by the season and climate. However, the measurement results obtained by the evaluation method provided by this application Less affected by season and climate.

Other embodiments of the invention will be readily apparent to those skilled in the art from consideration of the specification and practice of the invention disclosure herein. This application is intended to cover any modification, use or adaptation of the present invention, these modifications, uses or adaptations follow the general principles of the present invention and include common knowledge or conventional technical means in the technical field not disclosed in the present invention . The specification and examples are to be considered exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

The embodiments of the present invention described above are not intended to limit the protection scope of the present invention.

Claims (4)

1. a kind of grounding net of transformer substation performance estimating method injected based on ground line current, it is characterised in that methods described includes：

Substation parameters are obtained, calculating obtains the original diverting coefficient k of grounding net of transformer substation_e2；

Select an aerial earth wire of the transformer station, and the Injection Current I on the aerial earth wire_w, measurement access is described respectively The total current I of the circuit outflow of transformer station_w1The electric current I flowed out with transformer neutral point_N；

According to formula I_g=I_w-I_w1-I_NCalculating obtains the grounding net of transformer substation earth current I_g；

According to formula k_e1=I_g/I_wCalculating obtains the grounding net of transformer substation diverting coefficient k_e1；

Compare the diverting coefficient k_e1With original diverting coefficient k_e2, assess the security performance of the grounding net of transformer substation.

2. according to the method described in claim 1, it is characterised in that the acquisition Substation parameters, specifically include：

The transformer station includes n roots aerial earth wire and m telegram in reply cables, wherein, n >=1, m >=0.

3. method according to claim 2, it is characterised in that the total current of the circuit outflow of the measurement access transformer station I_w1, specifically include：

The electric current I of the n-1 roots aerial earth wire outflow of the measurement access transformer station_w2；

The electric current I of the m telegrams in reply cable outflow of the measurement access transformer station_w3。

4. according to the method described in claim 1, it is characterised in that the comparison diverting coefficient k_e1With original diverting coefficient k_e2, the security performance of the grounding net of transformer substation is assessed, is specifically included：

Calculate the diverting coefficient k_e1With original diverting coefficient k_e2Size variation amount；

If the diverting coefficient k_e1With original diverting coefficient k_e2Variable quantity be more than 20%, then judge that the grounding net of transformer substation can There can be failure；

If the diverting coefficient k_e1With original diverting coefficient k_e2Variable quantity be less than or equal to 20%, then judge that the transformer station connects Earth mat is functional.